Zinc deficiency: a problem with preterm breast milk.

We report a breast-fed preterm infant (31 weeks gestation) who developed nutritional zinc deficiency 13 weeks post delivery. Serial samples of his mothers breast milk from early lactation (2 weeks post delivery) contained very low zinc concentrations, although her serum zinc and sweat zinc concentrations were normal. Following the birth of her second baby at 38 weeks gestation, her breast milk contained normal amounts of zinc. We conclude that the low breast milk zinc values obtained following the first pregnancy may have been due to immaturity of the milk. Units that feed very low birth-weight babies preterm milk should check its zinc concentration or at least have a high index of suspicion for this nutritional deficiency.